Vagina itch. no yeast/bv or related stds. dr said she saw nothing of concern, just red vulva. what could cause this? extremely frustrating

Maybe still yeast: Your symptom still are suggestive of a yeast infection, which also is the main problem that would cause "red vulva" on exam. Yeast can be difficult to diagnose. It's still worth a try at treating for yeast. If that's been tried without effect, you could have a resistant type, needing atypical therapy. Discuss with your doctor, or see a gyn who also specializes in infections. Good luck!